i66 



THE PERMO-CARBONIFEROUS RED BEDS OF 



small. The bone resembles in many respects the one figured by Williston 

 (Bull. Geol. Soc.Amer.,vol. 21, pi. 15, figs. 4. a, b, c), but differs in the presence 

 of the process on the dorsal surface of the inner edge of the proximal end. The 

 articular faces, also, do not correspond with the figures given by Williston. 

 Nevertheless I am inclined to think that the bones are the same and that the 

 process mentioned has been lost in WilKston's specimen. 



Femur. — No. 3432 (fig. 38, d-g) is a small and rather heavy femur which is 

 evidently that of an amphibian but is not referable to any known form, unless 

 it belong to an immature Eryops. There is a deep bicipital fossa and a very 

 strong prominence on the inner edge near the middle of the shaft. The prox- 

 imal articular face is crescentic in outline, fiat, and confined to the end entirely. 

 The distal face is wide transversely and narrow antero-posteriorly ; the tibial 

 and fibular faces are undivided. If this is the femur of an immature Eryops 

 there must have been very considerable changes in the proportions of the 

 bone during development. The ridge on the anterior face would have to 

 become more prominent and the bone more elongate and slender. The speci- 

 men has been broken and crushed so that it is a little difficult to restore it 

 exactly, but an attempt has been made in the figure. 



UNASSIGNED FORMS, AMPHIBIA. 



There are three femora which are regarded as amphibian. It is noticeable 

 in the collection that the femora can be divided into two groups, one in 

 which the adductor ridge on the pos- 

 terior face crosses the shaft obliquely 

 and one in which the ridge is confined 

 to the inner edge and passes directly 

 downward to the distal end of the 

 bone. Those in which the ridge is 

 oblique are regarded as reptilian and 

 those with the ridge confined to one 

 side as amphibian. This seems to be 

 the most common arrangement in the 

 two groups, though in Ophiacodon the 

 ridge is confined to one side of the 

 bone. 



The first femur (No. 3298, fig. 39, a, 

 b, c) is regarded as probably amphibian 



because of the position of the adductor FiG- 39-— (a) inner edge, (6) lower face, (c) upper 

 ^■,Ar^^ ^U1,„. -u -w- 1 J- ■ ■, face of femur of right side of unnamed amphib- 



ndge, although its general form is that ian (?), No. 3298. x 5^. 



of a rentile Thp c;V|off io Trpt-ir 1/^-r.rr ^^A ^^^ ^°^^^ ^i^c, (e) proximal face, (/) distal face of 

 Oi a reptile, i ne snatt is very long and femur of right side of unnamed amphibian. No. 



slender and the ridge is very thin and ^'^^^' ^ ^• 



prominent. In this respect it resembles the femur from the Craddock bone- 

 bed figure by Williston (Amer. Perm. Vert., pi. xxxii, fig. 4), but differs 

 decidedly m the well-formed and very reptilian looking proximal and distal 



